Leubuscher recorded that in Jena the proportion of cases in the individual age classes did not correspond with the figures reported from other localities. Children, and especially very young children, suffered relatively less than adults.
The following statistics of the 1889–90 incidence of influenza among school children in Cologne were collected by Lent:
| Attendance. | Ill of influenza. | |||
|---|---|---|---|---|
| Class | I–13 | to 14 years of age | 3,002 | 1,015 33.8 per cent. |
| Class | II–11 | to 12 years of age | 5,737 | 1,835 31.9 per cent. |
| Class | III–10 | years of age | 3,701 | 1,130 30.5 per cent. |
| Class | IV– 9 | years of age | 3,590 | 930 25.9 per cent. |
| Class | V– 8 | years of age | 2,929 | 822 28.0 per cent. |
| Class | VI– 7 | years of age | 3,388 | 758 22.3 per cent. |
These may be compared with figures for the public schools in the suburbs of Cologne:
| Attendance. | Ill of influenza. | |||
|---|---|---|---|---|
| Class | I–13 | to 14 years of age | 1,609 | 689 42.9 per cent. |
| Class | II–11 | to 12 years of age | 2,885 | 1,094 37.9 per cent. |
| Class | III–10 | years of age | 1,683 | 626 37.1 per cent. |
| Class | IV– 9 | years of age | 1,758 | 552 31.4 per cent. |
| Class | V– 8 | years of age | 1,771 | 502 28.2 per cent. |
| Class | VI– 7 | years of age | 1,938 | 510 26.3 per cent. |
The increase of disease incidence with age is apparent. Finkler’s explanation for the higher incidence among the children of the suburbs, “that the children in the country had usually to walk a greater distance to school” does not appear to be complete.
Comby found that out of 3,411 school children in Lausanne 1,840 contracted influenza. This shows a relatively high incidence in children of school age in that city.
Concerning age distribution in 1889–90 Leichtenstern remarks that the greatest morbidity incidence was in school children, adolescents and young adults, especially the last. Nursing infants were attacked in considerably less degree than any of these other ages. Also in the higher ages those above sixty were attacked in lesser degree. The greatest morbidity frequently was between the ages of twenty and forty. Abbott concluded on the basis of estimates furnished him from various institutions and individuals in the State that people of all ages were attacked but the ratio of adults was greatest, of old people next, and of children and infants least.
Relationship of occupation to morbidity incidence.—Leichtenstern found that the only apparent influence of occupation on the incidence of influenza depended upon the liability to exposure in the various occupations. He remarks particularly on the large incidence of influenza among physicians. In contrast was the low incidence in lighthouse keepers. In 1889–90 among 415 dwellers on 51 lightships and 20 isolated lighthouses on the English coast only 8 persons developed influenza and these in four localities, and in every instance there was traceable direct communication from some other source. There is contradictory evidence as to whether individuals working out of doors are more apt to develop influenza. Certain statistics show that postmen and individuals working on railroads were attacked more frequently and earlier than others, while other statistics show that in railroads the office personnel was attacked earlier than individuals on the trains and those working on the tracks.
Abbott concluded that special occupations did not appear to have had a marked effect in modifying the severity of the epidemic. At the Boston Post Office in 1889–90, of the indoor employees, 475 in number, 25 per cent. were attacked. Of the carriers, 450 in number, 11 per cent. were affected with the disease. But there were other reports of the same period which stated that the ratio of the persons employed at outdoor occupations who were attacked was greater than that of indoor occupation.